Browsing by Author "Shin, Steven Seungjae"

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    Fundamental Mechanisms of Astrocyte and Cerebrovascular Regulation by Potassium in the Neocortex
    (2018-05-10) Shin, Steven Seungjae; Gordon, Grant Robert J.; Trang, Tuan; Bains, Jaideep Singh
    Astrocytes can control local cerebral arteriole tone through Ca2+ dependent mechanisms. Modest elevations of the external K+ concentration in the brain are thought to have little effect on astrocyte free Ca2+, yet K+ dilates parenchymal arterioles. It remains unclear whether fluctuations in external K+, within the low to moderate range, controls arteriole diameter through an astrocyte Ca2+ dependent mechanism. Using relative and quantitative two-photon fluorescence Ca2+ imaging in acute brain slices of the somatosensory cortex from Sprague Dawley rats, we found that elevations in external K+ from 2.5 mM to 3.5 or 5.0 mM decreased astrocyte free Ca2+ and caused arteriole dilation. The phenomenon relied on external Ca2+, Cl-, and bicarbonate, as well as, unexpectedly, the potassium chloride cotransporter (KCC). These data highlight novel aspects of K+-astrocyte dynamics that involve the subtle regulation of free astrocyte Ca2+ via Cl- and bicarbonate fluxes with corresponding changes to arteriole tone.